PROJECT SUMMARY/ABSTRACT Quantifying immune mediators within the cervicovaginal tract (CVT) enables researchers to assess women's susceptibility to HIV and other sexually transmitted infections (STIs). Nearly twenty studies have been published describing how immune factors in the CVT change during the menstrual cycle. Despite this abundance of data, we lack a clear picture of the immune changes that occur, and it remains completely unknown whether a specific phase in the menstrual cycle is associated with increased disease susceptibility. This knowledge gap has important implications for research on interventions to reduce STI risk in women. The primary goal of this project is to gain a comprehensive understanding of how menstrual cycle phase affects immune factor concentrations in the CVT. Our first aim is to perform a systematic review and meta-analysis of studies that have quantified immune mediators from CVT specimens during the luteal and follicular phases of the menstrual cycle in women who are not using hormonal contraception. Our preliminary data indicate that there are at least seventeen published studies meeting inclusion criteria. In addition to assessing variation during the menstrual cycle, we will also assess the impact of bacterial vaginosis, STIs (genital herpes, gonorrhea, and chlamydia), race/ethnicity, and age. We will address technical questions of key importance to the field, including the effect of CVT sample type, assay type, method of determining menstrual phase, and data normalization technique. Our second aim is to extend and validate the meta-analysis using samples from a cohort of 119 Kenyan adolescents ages 16-20 years (with a total of 200 samples). We will use preliminary results from our first aim to inform which immune factors we select for the Kenyan cohort, to both increase the number of immune factors that can be included in the meta-analysis and validate the most important findings. We then plan to add results of this aim to the meta-analysis. As we show in our preliminary data, by combining data from many studies, we can gain a comprehensive understanding of mucosal immune changes that impact women's susceptibility to STIs. Understanding these changes will provide an important foundation for future studies of health interventions (such as STI prevention strategies, HIV prophylaxis, or hormonal contraception) and drive future research in the basic immunology of the CVT.